Process and apparatus for correcting irregularities in the circularity of rings

ABSTRACT

A body such as a bearing race ring having a cylindrical outer surface is prevented from deforming during chilling to harden the body by rotating the body about its axis and engaging the outer surface of the body with at least two pressure rollers at two positions spaced circumferentially by 90* with respect to the center of the body. The load applied by the rollers may be increased progressively during chilling, or applied sharply after an initial period of free chilling of the body.

United States Patent Pettazzi Oct. 24, 1972 [54] PROCESS AND APPARATUS FOR 835,505 11/1906 Ehrhardt ..72/101 CORRECTING IRREGULARITIES IN 848,948 4/1907 White ..72/ 101 THE CRCULARITY 0F RINGS 2,617,466 11/ 1952 Kradoska ..72/ 101 3,000,426 9 1961 Drucker eta] ..72/1l0 [72] Invent Italy 3,230,606 1/1966 Saito eta] ..29/14s.4 [73] Assignee: RIV-SKF Officine de Villar Petosa 1,087,142 2/1914 Russell ..72/l10 S.p.A., Turin, Italy 1,753,963 4/1930 Mauser ..72/l10 [22] Filed July 1969 Primary Examiner-Milton s. Mehr [21] Appl. No.: 838,813 Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak 30 Foreign Application Priority Data [57] ABSIRACT A body such as a bearing race ring having a cylindrical July 11, 1968 Italy ..52399 A/68 outer surface is prevented from deforming during chilling to harden the body by rotating the body about its axis and g g g the outer Surface of the y [58] Id S 106 107 with at least two pressure rollers at two positions e 0 spaced circumferentially by 90 with respect to the center of the body. The load applied by the rollers [56] References Cited may be increased progressively during chilling, or ap- UNITED STATES PATENTS prlliectl stliiarply after an initial period of free chilling of t e O 3,464,253 9/1969 Beyer et a1 ..72/1 10 X y 1,930,562 10/1933 Krueger ..72/106 3 Claims, 2 Drawing Figures PROCESS AND APPARATUS FOR CORRECTING IRREGULARITIES IN THE CIRCULARITY OF RINGS The invention relates to a process and apparatus for correcting irregularities in the circularity of rings.

Hardening is known to result from the structural transformations occurring in a material during cooling of the material. The strains associated with these transformations produce, in general, appreciable deformation of the material. In the manufacture of precision annular bodies such as race rings for antifriction bearings, such deformations are inadmissible.

In order to avoid the deformations associated with hardening it is known to employ static mechanical devices to restrict the freedom of movement of the parts to be hardened during cooling thereof. Such devices are elaborate and expensive, and require in some instances the use of power presses. Moreover, such devices are expensive in operation because each part has to be formed separately.

Furthermore, satisfactory results are not always obtainable by this means because very high residual strains are nevertheless produced in workpieces being hardened.

An object of the present invention is to obviate the above drawbacks by providing a process which substantially relieves strains existing in a workpiece body both prior to hardening and during hardening, substantially avoiding deformation of the body.

A further object of the present invention is to provide means for correcting irregularly formed rings in which the irregularity arises by deformation during cooling.

The main characteristic feature of the process according to the invention is that deformations of the body upon chilling thereof are reduced by rotating the body about its axis while subjecting the said outer surface to the action of pressure rollers which engage the said surface at circumferentially spaced apart points to impart loads thereto in orthogonal directions so as to maintain the said surface substantially cylindrical during chilling of the body.

The invention further provides apparatus for carrying out the above described process, which is essentially characterized by the provision of two pairs of pressure rollers adapted to engage the outer surface of the body to be hardened in respective mutually perpendicular planes, one roller of each pair having a stationary axis, and the other roller of said pair having a displaceable axis to exert a load on the body, and means for rotating the body about its axis to bring all parts of said outer surface successively into contact with said pairs of rollers in order to reduce ovality of said body.

In both the process and apparatus the rollers having displaceable axes are moved inwardly to a final position in which the four rollers engage the truly circular ring at points located on two perpendicular diameters of the ring. The two movable rollers may be mounted on a common slide and the radial inward movement of the slide may take place progressively during chilling or may take place rather sharply after an initial period of free chilling of the body or ring.

The apparatus according to the invention is relatively simple and inexpensive in operation.

The invention will be more clearly understood from the following detailed description, given by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic plan view of apparatus according to one embodiment of the invention for reducing deformations clue to hardening of an annular or cylindrical body, and

FIG. 2 is a plan view similar to FIG. 1, illustrating a step of the process according to the invention during the restoration of a deformed annular body to its original circular profile.

The apparatus according to the invention includes two driving pressure rollers 2, 3 rotatable about fixed axes and carried by a stationary bedplate (not shown). The rollers 2, 3 are arranged to engage the outer surface of an annular or cylindrical body 1 to be hardened at two points spaced apart circumferentially by an angle of measured at the center of the body 1.

Both rollers 2, 3 and rotated in the same direction (clockwise as viewed in FIG. 1) by an external driving means (not shown) to cause rotation of the body 1 about its axis.

In addition to the driving rollers 2, 3 having fixed axes, the apparatus includes two movable idler pressure rollers 4, 5 freely rotatably mounted on a common slide 6. The slide 6 is movable along stationary guideways 7 in a radial direction with respect to the center of the body 1. An actuator 8, shown in broken outline, is effective to urge the slide 6 towards the axis of the annular body 1, in the direction of the arrow (FIG. 1).

The rollers 4, 5 are arranged to engage the outer surface of the annular body 1 at points spaced circumferentially by 90 from the points of contact with the body 1 of the respective adjoining rollers 3, 2. Thus the four pressure rollers from two pairs of rollers 2, 4 and 3, 5, the axes of which are situated in mutually perpendicular planes.

Upon rotation of the body 1 the two pairs of stationary and movable rollers 2, 4 and 3, 5 steadily circumscribe a circle.

Consequently, if the body 1 changes in diameter during chilling, while maintaining its circular form, it is merely stressed uniformly along a pair of orthogonal diameters at each angular position of the body by virtue of the rotation imparted thereto, so that, within the limits of accuracy of the apparatus, no deformation can be induced in the body 1.

Conversely, if the body 1 is initially deformed to an oval shape, as shown in FIG. 2, the two pairs of pressure rollers 2, 4 and 3, 5 will alternately stress the body 1 in the direction of its maximum diameter so that in the course of the rotation of the body the latter is deformed to cause it to assume a circular form, as indicated in broken outline in FIG. 2. At this stage the two pairs of pressure rollers 2, 4 and 3, 5 both contact the body 1 with similar pressures in two orthogonal directions, maintaining the circular form taken by the body 1 and preventing further deformation thereof.

The strength and manner of application of the load applied by the pressure rollers should in practice be dependent upon the size, shape and plasticity of the annular body 1.

It is important for the load applied by the movable pressure rollers 4 and 5 not to reach its maximum value while the annular body 1 is still at its highest temperature, as this might crush the body 1 owing to its high plasticity at this temperature. The load should therefore be applied gradually as the body 1 cools down. Alternatively, the load may be applied sharply at its maximum value after a short period of free chilling of the body 1, that is, chilling in the absence of loads.

It will be understood that constructional details of the invention may be widely varied from those of the embodiment specifically described and illustrated without departing from the scope of the invention as defined in the claims.

What is claimed is:

l. A high precision method for rendering an imperfectly circular ring having a constant cross-sectional thickness truly circular comprising the steps of rotating the ring between four rollers, two of which are mounted on a single common slide for movement in a radial direction with respect to the center of the ring in its final circular form and moving the slide under force radially inwardly to a final position in which the four rollers engage the truly circular ring at points located on two perpendicular diameters of the ring, said ring being unsupported on its interior wall throughout the operation, and the cross-sectional thickness of the material of the ring being maintained substantially unchanged.

2. A high precision apparatus for rendering an imperfectly circular ring having a constant cross-sectional thickness truly circular comprising four rollers between which the ring is adapted to be rotated, a single slide having cut-out means to provide clearance for a ring, said slide being movable in a radial direction with respect to the center of the ring in its final circular form, means mounting two of said rollers on said slide on opposite sides of said cut-out means for movement therewith, one such roller being mounted on each leg of said V-shaped end of said slide, and means for moving said slide radially inwardly under force to a final position in which the four rollers engage the truly circular ring at points located on two perpendicular diameters of the ring, said rollers being adapted to contact the external surface of the ring, said ring being unsupported within its interior cavity.

3. An apparatus as set forth in claim 2 further comprising means mounting the remaining two rollers for rotation about fixed axes. 

1. A high precision method for rendering an imperfectly circular ring having a constant cross-sectional thickness truly circular comprising the steps of rotating the ring between four rollers, two of which are mounted on a single common slide for movement in a radial direction with respect to the center of the ring in its final circular form and moving the slide under force radially inwardly to a final position in which the four rollers engage the truly circular ring at points located on two perpendicular diameters of the ring, said ring being unsupported on its interior wall throughout the operation, and the cross-sectional thickness of the material of the ring being maintained substantially unchanged.
 2. A high precision apparatus for rendering an imperfectly circular ring having a constant cross-sectional thickness truly circular comprising four rollers between which the ring is adapted to be rotated, a single slide having cut-out means to provide clearance for a ring, said slide being movable in a radial direction with respect to the center of the ring in its final circular form, means mounting two of said rollers on said slide on opposite sides of said cut-out means for movement therewith, one such roller being mounted on each leg of said V-shaped end of said slide, and means for moving said slide radially inwardly under force to a final position in which the four rollers engage the truly circular ring at points located on two perpendicular diameters of the ring, said rollers being adapted to contact the external surface of the ring, said ring being unsupported within its interior cavity.
 3. An apparatus as set forth in claim 2 further comprising means mounting the remaining two rollers for rotation about fixed axes. 